EP0964884A1

EP0964884A1 - Azeotropic or pseudo-azeotropic compositions and use of these compositions

Info

Publication number: EP0964884A1
Application number: EP98912415A
Authority: EP
Inventors: Pierre Barthelemy; Olivier Buyle; Pierre Dournel
Original assignee: Solvay SA
Current assignee: Solvay SA
Priority date: 1997-03-03
Filing date: 1998-02-21
Publication date: 1999-12-22
Anticipated expiration: 2018-02-21
Also published as: CZ9903125A3; SI0964884T1; WO1998039378A1; CA2283119C; DE69831059D1; SK285422B6; JP2001513838A; ATE301156T1; DE69831059T2; BR9808818A; SK120199A3; EP0964884B9; HUP0003832A2; AR011910A1; CZ297839B6; PL197803B1; ES2247687T3; HUP0003832A3; AU6726498A; US6303668B1

Abstract

The invention concerns 1,1,1,3,3-pentafluorobutane which forms azeotropic or pseudo-azeotropic compositions with alkanes having 5 or 6 carbon atoms. These compositions are used in particular as foaming agents in polymeric cell-closed foams.

Description

Azeotropic or pseudo-azeotropic compositions and use of these compositions

The invention relates to compositions comprising 1, 1,1,3,3-pentafluorobutane (also called HFC-365mfc) and the use of these compositions, in particular as swelling agents for polymeric cellular foams and more particularly for foams. polyurethane. It is well known that polyurethane foams can be prepared by reacting an isocyanate with an appropriate quantity of a polyol or of a mixture of polyols, in the presence of a swelling agent consisting of a volatile liquid, which is vaporized by the heat given off by the reaction between the isocyanate and the polyol. Trichlorofluoromethane (CFC-1 1), dichlorodifluoromethane (CFC 12) and, to a lesser extent, chlorodifluoromethane (HCFC-22), 1,1,2- trichlorotrifluoroethane (CFC-113) and 1,2-dichlorotetrafluoroethane (CFC-1 14) have long been used as blowing agents. Due to its very low thermal conductivity, CFC-11 makes it possible to obtain particularly insulating rigid polyurethane foams, which are used extensively as thermal insulators, in particular in the fields of building, refrigeration and transport.

However, fully halogenated chlorofluorinated hydrocarbons (CFCs) are suspected of causing environmental problems, mainly in the context of the destruction of the stratospheric ozone layer. They are now banned in most of their classic applications.

Chlorine-free hydrofluoroalkanes are completely inert vis-à-vis the stratospheric ozone layer and there is an increasing use of these compounds in many applications to the detriment of compounds carrying chlorine atoms. Thus, 1,1,1,3,3-pentafluorobutane (HFC-365mfc) has been proposed in various applications.

Japanese patent applications JP 05/168805 and JP 05/171190 describe solvent compositions comprising 1,1,1,3,3-pentafluorobutane, a cosolvent soluble in 1,1,1,3,3-pentafluorobutane and possibly a surfactant. These compositions can be used in object cleaning operations or for the elimination of waste water in the electronics industry. The the only binary compositions described include 4% n-pentane, 10% cyclopentane or 5% hexane.

Murphy et al. (International CFC and Halon Alternatives Conférence; Washington DC, 1993, pp. 346-355) described the use of binary cyclopentane / HFC-365mfc mixtures containing at least 54% by weight of cyclopentane as a blowing agent for foams polyurethane. However, it has been noted that F £ FC-365mfc and the mixtures mentioned above may, in certain cases and under certain circumstances, condense in the cells of the foam, causing, if necessary, a deterioration in its thermal conductivity and possibly its mechanical properties.

There is still a need to find blowing agent compositions for polymeric cellular foams devoid of any harmful effect on the environment, having a boiling point close to the boiling point of CFC 11 or 1,1-dichloro-1 -fluoroethane (HCFC-141b) and having the physical properties which make it possible to form polymeric cellular foams of low thermal conductivity in a wide range of temperatures, particularly closed cell foams and of homogeneous size.

One of the objects of the present invention is to provide compositions which are particularly effective when used as blowing agents, in particular for the manufacture of polyurethane foams. Another object of the invention is to provide such compositions devoid of destructive effect with respect to the ozone layer and therefore usable as a replacement for compositions based on completely halogenated chlorofluoroalkanes such as CFC-11 or d partially halogenated hydrocarbons containing chlorine atoms such as HCFC-141b.

The present invention therefore relates to compositions essentially consisting of 1,1,1,3,3-pentafluorobutane and an alkane having 5 or 6 carbon atoms which are characterized in that they are azeotropic or pseudo-azeotropic. Basically, the thermodynamic state of a fluid is defined by four interdependent variables: pressure (P), temperature (T), composition of the liquid phase (X) and composition of the gas phase (Y). A true azeotrope is a particular system with 2 or more components for which, at a given temperature and at a given pressure, the composition of the liquid phase X is exactly equal to the composition of the gas phase Y. A pseudo-azeotrope is a 2 or more component system for which, at one given temperature and at a given pressure, X is substantially equal to Y. In practice, this means that the constituents of such azeotropic and pseudo-azeotropic systems cannot be easily separated by distillation and therefore their composition remains constant in the operations of inflation of polymeric cellular foam.

For the purposes of the present invention, the term pseudo- azeotropic mixture is understood to mean a mixture of two constituents whose boiling point (at a given pressure) differs from the boiling point of the true azeotrope by 0.5 ° C. maximum. Mixtures whose boiling point differs from the boiling point of the true azeotrope by a maximum of 0.2 ° C are preferred. Mixtures whose boiling point differs from the boiling point of the true azeotrope by 0.1 ° C maximum are particularly preferred.

The alkanes having 5 or 6 carbon atoms which can be used in the compositions according to the invention can be linear, branched or cyclic. Among all the possible isomers of hydrocarbons having 5 or 6 carbon atoms, linear pentane (or n-pentane), isopentane (or 2-methylbutane), cyclopentane and linear hexane (or n-hexane) are preferred. . These form, with 1,1,1,3,3-pentafluorobutane, azeotropic or pseudo- azeotropic compositions with minimum boiling point. The azeotropic and pseudo-azeotropic binary mixtures formed between 1,1,3,3,3 -pentafluorobutane and cyclopentane are particularly preferred. The relative contents of 1,1,1,3,3-pentafluorobutane and alkane having 5 or 6 carbon atoms in the compositions according to the invention can vary within wide proportions provided that the compositions thus formed are azeotropic or pseudo- azeotropics with minimum boiling point.

The compositions of the azeotropic mixtures according to the invention were estimated by calculation based on the results of the experimental measurements presented in the examples below.

1,1,1,3,3 pentafluorobutane and n-pentane form an azeotrope or a binary pseudo-azeotrope when their mixture contains approximately 24 to 60% by weight of n-pentane. Binary compositions containing about 30 to 53% by weight of n-pentane are preferred. Binary compositions containing about 32 to 47% by weight are particularly preferred. Under a pressure of 103.5 kPa, the binary composition consisting essentially of approximately 66% by weight of 1,1,1,3,3 pentafluorobutane and approximately 34% by weight of n-pentane constitutes a true azeotrope, the boiling point of which is approximately 27.4 ° C. This composition is very particularly preferred.

1,1,1,3,3 pentafluorobutane and cyclopentane form an azeotrope or a binary pseudo-azeotrope when their mixture contains approximately from 16 to 46% by weight of cyclopentane. Binary compositions containing about 18.5 to 39% by weight of cyclopentane are preferred. Binary compositions containing about 20 to 35% by weight of cyclopentane are particularly preferred. Under a pressure of 101.4 kPa, the binary composition consisting essentially of approximately 78.5% by weight of 1,1,1,3,3 pentafluorobutane and approximately 21.5% by weight of cyclopentane constitutes a true azeotrope , whose boiling point is around 32.2 ° C. This composition is very particularly preferred.

1,1,1,3,3 pentafluorobutane and isopentane form an azeotrope or a binary pseudo-azeotrope when their mixture contains approximately 31 to 75% by weight of isopentane. Binary compositions containing about 39 to 70% by weight of isopentane are preferred. Binary compositions containing about 45 to 60% by weight of isopentane are particularly preferred. Under a pressure of 101.2 kPa, the binary composition consisting essentially of approximately 53% by weight of 1,1,1,3,3 pentafluorobutane and approximately 47% by weight of isopentane constitutes a true azeotrope, the boiling point is around 22.5 ° C. This composition is very particularly preferred.

1,1,1,3,3 pentafluorobutane and n-hexane form an azeotrope or a binary pseudo-azeotrope when their mixture contains approximately from 6 to 29% by weight of n-hexane. Binary compositions containing about 9.5 to 24% by weight of n-hexane are preferred. At a pressure of 102.1 kPa, the binary composition consisting essentially of approximately 90% by weight of 1,1,1,3,3 pentafluorobutane and approximately 10% by weight of n-hexane constitutes a true azeotrope, of which the boiling point is around 37.9 ° C. This composition is very particularly preferred. The invention also relates to the use of the compositions according to the invention for the inflation of polymeric cellular foams.

Polymeric cellular foams can be obtained by various methods. A commonly used method consists in injecting under pressure a blowing agent into a molten polymer mixture to be expanded in an extruder. The decompression obtained at the outlet of the extruder leads to the expansion of the polymeric mixture with the formation of a foam consisting of cells filled with the blowing agent. Polystyrene foams are generally obtained by this process. Another method, typically used to make polyurethane or polyisocyanurate foams, is to react an isocyanate with an appropriate amount of a polyol or a mixture of polyols, in the presence of a blowing agent consisting of a liquid. volatile, which is vaporized by the heat given off by the reaction between the isocyanate and the polyol. The compositions according to the invention are particularly recommended for the inflation of polyurethane or polyisocyanurate foams, very particularly for manufacturing rigid foams. In this case, use is generally made of 1 to 40, typically 15 to 35 parts by weight of blowing agent per 100 parts by weight of polyol.

The invention also relates to blowing agents for polymeric cellular foams, which are characterized in that they contain an azeotropic or pseudo-azeotropic composition according to the invention. The blowing agents containing a composition according to the invention consisting of 1,1,1,3,3-pentafluorobutane and cyclopentane are particularly suitable for the preparation of polyurethane or polyisocyanurate foams.

In a variant according to the invention, the blowing agents also contain n-butane or isobutane, typically from 2 to 20% by weight, preferably from 5 to 15% by weight.

The blowing agents for polymeric cellular foams may also contain a stabilizer of the azeotropic or pseudo-azeotropic composition according to the invention, such as nitromethane or alpha-methylstyrene.

The azeotropic or pseudo-azeotropic compositions according to the invention can be used in premixtures for polyurethane or polyisocyanurate foams. Such premixes contain at least one polyol, an azeotropic or pseudo-azeotropic composition according to the invention and optionally various additives usually used to prepare polyurethane or polyisocyanurate foams such as in particular water, catalysts, surfactants, antioxidants, flame retardants and / or pigments. The premixes containing the azeotropic or pseudo-azeotropic compositions according to the invention also form part of the present invention. The invention also relates to the use of the azeotropic or pseudo-azeotropic compositions described above as refrigerants, as solvents, as desiccants or as degreasers for solid surfaces. The following non-limiting examples illustrate the invention in more detail. Examples 1-4

To demonstrate the existence of azeotropic or pseudo-azeotropic compositions according to the invention between 1,1,1,3,3 pentafluorobutane and a hydrocarbon having 5 or 6 carbon atoms, a glass apparatus consisting of '' a 50 ml boiling flask topped with a reflux condenser. The temperature of the liquid was measured using a thermometer immersed in the bottle.

A quantity of 1,1,1,3,3 pure pentafluorobutane determined with precision was heated under a known pressure until boiling, then small quantities of hydrocarbon, weighed with precision, were gradually introduced into the bottle by means a syringe, via a side tube.

The determination of the pseudo-azeotropic compositions was carried out by recording the evolution of the boiling temperature of the mixture as a function of its composition.

These measurements were carried out for mixtures containing 1,1,1,3,3-pentafluorobutane and increasing amounts of n-pentane (example 1), cyclopentane (example 2), isopentane (example 3) or n-hexane (Example 4).

The pressure at which the measures were taken is mentioned. The evolution of the boiling point of the different compositions as a function of their hydrocarbon content, expressed in% by weight, is presented in Table I.

Table I

Examples 5-8

Polyurethane foams were prepared from the same formulation, but using as blowing agent either F £ FC-365mfc (example 5), cyclopentane (example 6), a composition FfFC-365mfc / cyclopentane made up, by weight, 72 parts of FLFC-365mfc and 28 parts of cyclopentane (example 7) and a composition HFC-365mfc / n-pentane, consisting, by weight, of 58.4 parts of HFC-365mfc and 41.6 parts of n-pentane (Example 8). The thermal conductivity (Lambda) of these foams was then measured at different temperatures. The variations in thermal conductivity are presented in Table II. The thermal conductivity, measured at 24 ° C., of a foam obtained with rTFC-365mfc was taken as a reference. The variations are expressed in percent compared to this reference. A positive variation corresponds to an increase in conductivity, that is to say a decrease in the insulating power of the foam.

Table II

While the thermal conductivity in the gas phase of cyclopentane is higher than that of HFC-365mfc (respectively 12 and 10.6 mW / mK at 25 ° C), a polyurethane foam swollen with the azeotropic mixture 1.1, 1, 3, 3 -pentafluorobutane / cyclopentane has a low thermal conductivity at low temperature than that of a comparable foam swollen with HFC-365mfc, in the absence of cyclopentane.

Similar results are obtained with the azeotropic composition HFC-365mfc / n-pentane.

Claims

R E V E N D I C A T I O N S

1 - Composition essentially consisting of 1, 1, 1,3,3-pentafluorobutane and a hydrocarbon containing 5 or 6 carbon atoms characterized in that it is azeotropic or pseudo-azeotropic.

2 - Composition according to claim 1 in which the hydrocarbon containing 5 or 6 carbon atoms is chosen from n-pentane, cyclopentane, isopentane and n-hexane.

3 - Composition according to claim 2 containing about 24 to 60% by weight of n-pentane or about 16 to 46% by weight of cyclopentane or about 31 to 75% by weight of isopentane or about 6 to 29% by weight of n -hexane.

4 - Composition according to claim 3 containing about 30 to 53% by weight of n-pentane or about 18.5 to 39% by weight of cyclopentane or about 39 to 70% by weight of isopentane or about 9.5 to 24% by weight of n-hexane.

5 - Composition according to claim 4 containing about 32 to 47% by weight of n-pentane or about 20 to 35% by weight of cyclopentane or about 45 to 60% by weight of isopentane.

6 - Azeotropic composition with minimum boiling point according to claim 5, composed of approximately 66% by weight of 1,1,1,3,3-pentafluorobutane and approximately 34% by weight of n-pentane, the boiling point is approximately 27.4 ° C under a pressure of 103.5 kPa.

7 - Azeotropic composition with minimum boiling point according to claim 5, composed of approximately 78.5% by weight of 1,1,1,3,3-pentafluorobutane and approximately 21.5% by weight of cyclopentane, whose boiling point is approximately 32.2 ° C under a pressure of 101.4 kPa.

8 - Azeotropic composition with minimum boiling point according to claim 5, composed of approximately 53% by weight of 1,1,1,3,3-pentafluorobutane and approximately 47% by weight of isopentane, the point of which d boiling is around 22.5 ° C under a pressure of 101.2 kPa.

9 - Azeotropic composition with minimum boiling point according to claim 4, composed of approximately 90% by weight of 1,1, 1,3,3- pentafluorobutane and about 10% by weight of n-hexane, whose boiling point is about 37.9 ° C under a pressure of 102.1 kPa.

10 - Use of the azeotropic or pseudo-azeotropic compositions according to any one of claims 1 to 9 for the inflation of polymeric cellular foams.

1 1 - Use according to claim 10 characterized in that the polymeric cellular foam is a polyurethane or polyisocyanurate foam.

12 - Blowing agent for polymeric cellular foams characterized in that it comprises an azeotropic or pseudo-azeotropic composition according to any one of claims 1 to 9.

13 - Premix for polyurethane foam characterized in that it comprises an azeotropic or pseudo-azeotropic composition according to any one of claims 1 to 9, at least one polyol and possibly various usual additives.

14 - Use of the compositions according to claims 1 to 9 as refrigerants, as solvents, as desiccants or as degreasing agents for solid surfaces.